1. Field of the Invention
The present invention relates to the field of electrical connectors, and more particularly to a two-part connector shell assembly which enables the use of a specialized retainer clip. Due to the ability to open the connector shell assembly for insertion of the clip, the clip can be attached to the shell assembly in a manner which provides easy and precise alignment. Further, the clip design provides for load distribution in a manner which reduces stress fatigue.
2. Brief Description of the Background Art
Electrical connectors are available in a multitude of different designs, to serve a broad base of requirements. A frequently used design includes a plug and receptacle, each of which includes a contact or terminal module, including a dielectric housing in which contacts or terminals are secured; and a shell member surrounding the housing for physical protection and also for shielding and grounding purposes. Conventional methods for securing the contact module within the protective shell include the use of adhesive materials, locking rings, or other retention hardware.
Examples of electrical connectors which are useful in the applications for which the present connector is useful are described below, to provide a background for the present improved connector.
U.S. Pat. No. 3,993,394 to James Cooper, issued Nov. 23, 1976, discloses a connector half having substantially parallel transverse walls joined by perpendicular sides to provide a substantially rectangular cross-section to receive at least one flat connector wafer inserted therein in a forward axial direction. A transverse rib is formed on an upper face of a wafer facing an inner face of a connector transverse wall. A spring clip cantilevered on the inner face of the connector half is provided. When the wafer is inserted into the connector half, the rib acts as a cam against the spring clip, forcing the spring clip up. The spring clip returns to abut the rear of the rib as the wafer is pushed into position, to retain the wafer in the connector half. A tool is provided for camming the spring clip to allow removal of the wafer.
U.S. Pat. No. 4,619,490 to Robert Hawkings, issued Oct. 28, 1986, describes a guidance and retention device for terminated connector wafers having a housing and at least one pair of opposed wafer retention members, said members releasably secured to opposed walls of the housing to provide the guidance and retention of rectangular-shaped connector wafers therebetween. The wafer retention members are described as being easily relocated to allow for reorganization of connector wafers and of a wiring array. In particular, these retention members comprise one member releasably connected to a first opposed wall and the other member releasably connected to a second opposed wall, each member having a plurality of guidance portions and retention portions which guide conductor wafers which are inserted in a stacked relationship within the housing.
U.S. Pat. No. 4,764,130 to Thomas DiClemente, issued Aug. 16, 1988, discloses an electrical connector having a retaining member which has a transverse section seated in an aperture in the connector housing. The forward end of the retaining member is folded back on itself and fits into an opening in the connector housing. A pair of retaining legs extend outwardly from the transverse section to engage an inside surface of the connector housing; these retaining legs work in cooperation with the folded member to hold the retaining member in position within the connector housing. In addition, a second pair of retaining legs extend inwardly into the connector housing passageway to retain the terminal housing in position within the connector housing. The metal shell (connector housing) which surrounds the terminal housing is of a single piece construction, and is used in combination with retaining members are formed from a metal as well, and are described as being stamped and formed from a material having desirable spring characteristics, such as, for example, stainless steel.
U.S. Pat. No. 4,927,388 to David Gutter, issued May 22, 1990 discloses a single piece protective shell of an electrical connector which includes clip members affixed to the inside of the protective shell, with spring arms of the clips extending forwardly and inwardly to latch behind transverse ribs along the outwardly facing surfaces of the terminal modules inserted into the shell. Each clip includes a pair of outwardly directed tabs along lateral edges of the body section, and the tabs are inserted outwardly through associated longitudinal slits in the shell wall and then bent over along the outward surface of the shell, preferably into recesses to be flush with the outward shell surface. A pair of such clips along the upper inside surface and along the lower inside surface cooperate to retain a pair of terminal modules inserted into the shell.
U.S. Pat. No. 5,125,854 to Bassler et al., issued Jun. 30, 1992 describes an electrical connector assembly which includes a shield and frame member wherein at least a portion thereof is conductive. A plurality of modular sub-assemblies is mounted in the assembly. A latch mechanism is provided for removably securing each modular sub-assembly to the shield and frame member. The latch mechanism includes a tab which extends from the shield and frame member, wherein the tab has a slot which fits over a projection on the modular sub-assembly.
U.S. Pat. No. 5,145,411 to Pastal et al., issued Sept. 8, 1992, describes a dielectric insert of an electrical connector retained within a metal shell by a plurality of latching ledges formed integrally with the insert member. The ledges are spaced about the periphery of the outer surface of the insert member, and during insertion into the shell member, these ledges are engaged with corresponding stop surfaces defined along inside surfaces of the metal shell.
Many of the electrical connectors described above find use in airline applications, and particularly for signal transmission applications. Due to the criticality of reliable performance, the connectors must meet stringent requirements. The exterior of the connector (the shell) is typically conductive and provides electromagnetic shielding. The connector as a whole is tested for mechanical durability, resistance to chemicals and to salt spray. For example, airline connectors are tested for vibration resistance per military standard MIL-STD-1344, which requires that there be no damage or electrical discontinuity after vibration testing.
In addition to the requirements for the exterior shell, the connector must provide a means of securing terminal modules within the shell. The means for securing the module should not interfere with insertion of the module into the shell, should not expose the securing means to the exterior environment in a manner which may cause the securing means to fail, and should provide for a careful alignment of the modules within the shell. This latter feature ensures proper electrical engagement within the connector.
Not only must the connector meet the technical requirements specified above, but as always, the cost of manufacturing the connector is an important consideration.
The present electrical connector assembly includes an outer shell capable of receiving at least one electrical contact module The outer shell works in cooperation with an improved contact module retaining device which secures the electrical contact module within the shell. The combination of the outer shell with the module retaining device protects the critical elements of the retaining device from exterior environments, does not interfere with insertion of the contact module into the shell, and provides for a precise alignment of the module during and after insertion of the contact module into the shell.
In particular, a complete electrical connector includes both a plug and a receptacle, and the following description applies to each. The outer shell is comprised of two halves which are open during attachment of a contact module retaining device to each half shell. The two halves are closed after attachment of the contact module retaining device. Preferably, the shell halves, with contact module retaining device in place, are permanently riveted into the closed configuration. A tool is provided which permits easy release of a contact module, if necessary. Typically the outer shell is rectangular in shape and is fabricated from aluminum which is cadmium or nickel plated, depending on the end use application. Preferably the shell halves are cast (using standard casting techniques) rather than machined, to reduce costs. The closed, assembled shell with module retaining device in place is capable of encompassing at least the portion of a contact module which contains the contacts and is capable of retaining the module after insertion into the assembled shell.
The preferred retaining device which secures the electrical contact module within the shell is a clip. In the preferred embodiment, a clip is attached so that the main body of the clip is in contact with an interior surface of each half of the outer shell. When a contact module (which is generally rectangular) is inserted into the connector assembly, the contact module is held in place by a clip on each opposing side (exterior surface) of the module. Initially (prior to closing of the half shells to form an assembled shell with module retaining device) each clip is attached to the half shell by a snap fit. After the shell is closed and riveted (or otherwise fastened together), the clip is entrapped by the walls of the shell and is secured at the proper position by contact with the surfaces of the closed shell.
The retaining clip snap fit includes four (4) mechanical contact points which snap into place and a fifth contact point which is an insert shape which extends through an opening in the half shell and is subsequently bent or folded to lie flat within a recession on the exterior of the half shell. Two of the snap fit contact points work in conjunction with the insert to align and secure the clip against a half shell interior surface relative to the leading end and trailing end of the connector. The remaining two of the snap fit contact points align and secure the clip against the shell half interior surface relative to the side edges of the connector, which together with the leading and trailing ends form the rectangular connector body. The side edge snap fit contact points secure the clip so that it cannot become canted at an angle from side edge to side edge of the shell. This five point positioning (alignment and securing) of the retaining clip within the half shell interior ensures proper alignment of the clip prior to joining together of the two half shells. After joining of the two half shells, the clip is trapped in the proper alignment, ensuring proper alignment of the contact module upon insertion into the shell. This proper alignment is critical in ensuring proper electrical engagement between contact modules when two electrical connector assemblies are joined to produce an electrical connection.
Due to the rectangular shape of the preferred embodiment connector and the accurate alignment of the retaining clip within the connector shell, an entirely parallel alignment of connecting electrical contact modules is obtained. This parallel alignment enables proper electrical engagement and ease in sealing of the electrically engaged contact elements from the environment.
The use of two half shells each having a module retaining clip attached thereto gives rise to a particular method of fabricating an electrical connector assembly, the method comprising:
a) snap fitting a retention clip into contact with an interior surface of a half shell while simultaneously inserting a protrusion from the clip surface through an opening in the half shell;
b) mechanically securing the protrusion to the exterior surface of the half shell;
c) joining two half shells together to form an assembly comprising an exterior shell having a protective outer surface, with a contact module retaining device on the interior surface of each half shell, wherein the assembly is capable of encompassing at least the portion of an inserted contact module, and is capable of retaining the contact module after its insertion into the assembly.
Preferably the snap fitting of the contact module retention clip to the half shell occurs by snap fitting of a first pair of snap fit points which secure the retention clip in the direction of the leading and trailing edges of the connector. Preferably the snap fit points are in the form of pre-bent tabs extending from the upper surface of the clip. The upper surface of the clip is placed adjacent to the interior surface of the half shell, and the pre-bent tabs slide into position against the half shell through openings in the half shell and rest against recessed surfaces on the exterior surface of the half shell. As the pre-bent tabs slide into position, an insert shape, which is preferably a substantially straight tab, is inserted through an opening in the shell, to extend up through to the exterior of the half shell. This provides a three point alignment and a secure attachment of the retention clip to the half shell in the direction from leading edge to trailing edge of the connector assembly. A second pair of snap fit points, which align and secure the retaining clip against the shell half interior surface relative to the side edges of the connector is then snapped into place against the half shell interior surface. Preferably the second pair of snap fit points are in the form of bent arms which snap over a step along the edge of each half shell. Subsequent to snap fitting the second pair of snap fit points, the insert shape (tab) is bent into place against the exterior surface of the half shell, preferably bent into a recessed area on the surface of the half shell. The final result is five point positioning of the retention clip which aligns and secures the clip within the half shell.